Beta-hydroperfluoroalkyl compounds of phosphorus



Patented July 31, 1'9-32 3,047 619 snrA-nYnRorunrLUoaoALKYL comoimns or rnosrnonus Neal 0. Brace, Wilmington, DeL, assignor to E1. du

This invention relates to beta-hydroperfiuoroalkyl compounds of phosphorus and more particularly to betahydroperfluoroalkyl phosphinic acids and beta-hydroperfiuoroalkyl phosphonic acids and their salts and to the process for preparing such acids.

Fires, involving petroleum hydrocarbons, aromatic hydrocarbons and other materials which are at the same time insoluble in water and less dense than water, have always posed a very serious problem. Dueto their insolubility and lesser density, these 'materials float on water. Therefore, the-usual system of fire fighting, in volving a stream of water ejected from a hose or similar conduit, has been of little use with these materials since the fire is not smothered. In fact, more harm than good often has been the result since the burning liquids often spread on the water and cover a wider area than originally was the case.

Several methods are now used in attempts to overcome tlciis problem. Two methods based on water involve a f g created by a special nozzle or a foam created by adding certain materials to water and dispensed with special equipment. While both of these methods of fire fighting have enjoyed success in certain situations, their usefulness is limited. It is necessary, in both cases, to approach the immediate vicinity of the source of thefire to apply the extinguishing agentb'ecause the'fo'g or foam cannot be projected over a long distance as can a stream of water. This necessary approach creates a hazard to the fire fighting personnel. The area that can be covered by these methods is also limited so that large scale fires are not readily brought under control.

The other methods are based on nonaqueous systems. Three classes of extinguishing agents are used: gases, liquids and solids. The gases, carbon dioxide or certain brominated methanes such as bromotrifiuoromethane, are limited to relatively small fire situations. Again, to be effective, these materials must be released at the source of the fire and must cover the entire fire. Like the fog and foam, they cannot be projected into a fire from a safe distance. Being gases under pressure, these materials must be stored and transported in heavy steel cylinders.

The liquids, e.g. carbon tetrachloride or chlorobromomethane, must be transported to the scene of a fire. They are also limited to small fires because of the volumes of materials required. They can be projected over some distance but most of the liquid extinguishing agents have fallen into disfavor because of the toxic nature of the materials or of their decomposition products.

The third class, solids, is composed of materials such as sodium bicarbonate. The solids, in the form of a very fine powder, are projected by means of a compressed gas into the fire. pressed gas-must be transported, the system is limited. The solids cannot be projected over too great a distance. Also, they must blanket the entire fire to be effective.

It is apparent from the foregoing discussion that fire extinguishing agents are needed which will be effective against fires involving hydrocarbons and similar materials, which do not have to be stored and transported in large volume to the scene of the fire, which can be projected over a sufficient distance so that the fire fighters need not approach the fire themselves, and which need Since both the solid material and the com- An obvious solution would be to provide a material which can be added to water so that the water will meet the requirements cited above. Although a great deal of re search has been conducted on the search for materials to provide this obvious solution, the search has been completely unsuccessful. It has been theorized that a surface active agent, which would convert water to a mixture that would mix with and wet hydrocarbons, was necessary. Hydrocarbon based surface active agents were completely unsuccessful, as were the somewhat more efiicient surface active agents H[CF CF PO(OH) Even the very highly active and somewhat spectacular perfiuoroalkyl surface active agents C F CO H,

c r so u and C F CONH(CH N(CH I were not successful in solving this problem.

It is an object of this invention to provide new and improved surface active agents. Another object is to provide substances which can be added to water to render it effective for extinguishing fires, particularly fires involving hydrocarbons and similar materials. A further object is to provide aqueous solutions which can be projected over fairly long distances for extinguishing hydronot blanket the entire fire simultaneously to be eifective.

carbon and like fires and which are effective for that purpose without simultaneously blanketing the entire fire. A still further object is to provide substances which can be stored and transported in small volume and added to water at the scene of a fire. Other objects are to provide new phosphorus acids and their salts and to advance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished in accord with this invention which comprises compounds of the formula wherein n is an integer of from 2 to 5, X represents a member of the group consisting of H and OZ, and Z is a member of the group consisting of H, Na, and K; and aqueous solutions of from about 0.1% to about 1% by weight of such compounds which are valuable fire extinguishing compositions, particularly for fires involving hydrocarbons and like materials.

It has been found that the compounds of the above formula are new and improved surface active agents and are useful as chemically stable organic acids and salts. The free acids are strong acids resembling mineral acids, and their salts resemble typical salts of strong acids. The acids and the salts are soluble in water and in hydro carbons, halogenated hydrocarbons, and many other organic solvents. Most particularly, aqueous solutions of such acids are very effective to extinguish fires involving hydrocarbons, such as gasoline and other petroleum products, benzene, and like materials which are lighter than and immiscible with water, when such aqueous solutions are sprayed on such tires from an ordinary hose nozzle or any other suitable means. The ability of aqueous solutions to extinguish fires of such character appears to be unique with the acids of this invention.

In light of the fact that aqueous solutions of other surface active agents, including the best prior perfluoroalkyl surface active agents, would not extinguish fires involving hydrocarbons or similar materials, it was completely unexpected that aqueous solutions of the compounds of this invention in the free acid form Would extinguish such fires. Aqueous solutions of these acids wet and mix with hydrocarbons, as do aqueous solutions of some of the prior perfluoroalkyl surface active agents, but the solutions of the acids of this invention are the only ones known that act as fire'ex-tinguishing agents when applied to a hydrocarbon fire as an ordinary stream of is more efiicient than the other types of fiuorinated surface water. .The concentration of material necessary to proactive agents in lowering aqueous surface tensions and duce the effect may vary somewhat with the length of the that the similar agent CF (CF CHFCF PH(O) (ONa), polyfluoroalkyl chain, decreasing somewhat with increase while less eflicient than the previous example, is neverin the chain length. Aconcentration of from about 0.1% theless more eflicient than the other types. Thus, the to about 1% by Weight of an a of this invention is facids and salts of this invention are unexpectedly found to ficient to produce the desired effect. Usually, it is prebe more eflicient-than any other known type of fluoriferred to employ a concentration of from about 0.5% to nated, anionic surface active agent. about 1% y Weight of the acid based on the Watef- The acids of this invention are also effective in reducing The acids of this invention find ready application in the surface tension of hydrocarbons and chlorinated hysituations where large volumes of hydrocarbons or simid o b n Th a 0.043 wt, percent solution of lar materials are stored, where water itself is readily CF (CF CHFCF P(O)(OH) i be e lowered the available at every location but where the other special fa t n i b even dynes/crn. In comparison, extinguishing agents described previously are ineffective C F SO H t 01% o t ti i b e, l wer d or where storage and/or transport of such other mateth Surface t i only 5 6 d A ()8 Wt rials is uneconomical or inconvenient. Such situations t l i fQF (c1-T 4CHFCFZP(O) 0H) i 1 1 2- would include l refineries. chemical Plants using or trifiuoro-1,2,2-trichloroethane (CF Cl- -CF Cl lowered manufacturing large Volumes of benzene, eikyl beIlZeIleS, the surface tension by 2.5 dynes/cm. Considering that styrene or similar materials. or on certain Ships Such as the initial surface tension was 17.6 dynes/cm., any lowertankers which transport petroleum or other flammable ing is remarkable. Chemical materials- The acids and salts of this invention can be applied to The equipment necessary to add the Subject acids to many of the uses known for perfluoroalkyl surface active Water Stream Will be y pp n to those Skilled in agents. These uses include evaporation inhibition for the and is reasonably inexpensive and not Space 0011- gasoline, improving the surface protection, flow, spread- Sumilig- It can easily be installed in the P p truck ing penetration andatomization or sprayability of petroof a fire control system or in the fire control system of a leum hydrocarbons, and f wax emulsions, h can ship. Storage of the acids of this invention poses no problem since only about one pound of acid per 1000 pounds of water is necessary. Since the acids are very dense, the storage volume is low; a quart of the acid weighs about four to five pounds.

The reason why the subject acids produce this desired be used as surface active agents for strongly corrosive or highly oxidizing media such as pickling baths, electroplating baths and in such strong acids as 98% sulfuric acid, nitric-hydrofluoric acid mixtures or red fuming nitric acid. They can be used as emulsifying agents for effect while other perfiuoroalkyl surface active agents do fluorocarbon-oil fiuorocarbon'water Systems and for not is not understood systems containing the chlorofluorocarbon propellants Besides the unique property described above the acids 3 used in aeroso applications. These acids and salts are and salts of this invention are excellent surface active also useful as emulsifying agezits for Polymerizations, P

agents for many liquids. Given in the table below is a iicuiariy these involving fiuofllleied Oleiillscomparison of some of the preferred compounds wherein The beifl-hydfepeffiuel'eeikyi acids of Phosphorus and n is 4, with several other surface active agents containing their salts of this invention are readily prepared by reactperfiuoroalkyl groups of similar size. For comparison, 4 ing aperfiuoroolefin of the structure CF (CF ),,CF=CF the surface tension of water at 25 C. is 72 dynes/crn. with a phosphorus compound of the structure TABLE Surface Tensions In Water H(CF2CF2)4P(O)(OH)1 C7F 5CO2H CgFnSOaH 41 oraonrorirowun 39 The data, from which the table was derived, indicate f that all of these agents had reached their ultimate lower- 0 ing of surface tension at 1.0% concentration. The ad- Y vantage of all of these agents except in the presence of a free-radical initiator at a tempera- I-IF(31-1 110( ture of from about 50 C. to about 200 C. The perfluoroolefins are readily obtained by the pyrolysis of perover hydrocarbon containing agents 15 apparent smce fluorinated id f th formula CF (CF ),,CF CF CO H agents containing hydrocarbon groups reach their uitior their sodium salts, which acids are well known and mate lowering of surface tensions of water solutions at commercially available The phosphorus compounds f I 28-30 dynes/ cm. The compound CF CHFCF PO(OH) h f l illustrates the properties of compounds similar to the subject compounds but outside the range of this invention. i

This latter compound compares very unfavorably with the 0 compounds of this invention. Aqueous solutions of CF CHFCF PO(OH) have no fire extinguishing properties for hydrocarbon fires.

I H PO alkali hypophosphites such as SOdlUIIl hypophos- It IS aPPa-mnt from table that phite, NaH PO alkali phosphites such as Na HPO and CF (CF CHFOF PO(OH) the lower alkyl, aryl, and halo aryl esters of hypophosinclude hypophosphorous acid, I-I PO phosphorous acid,

, r phorous acid and phosphorous acid, represented by methyl hypophosphite, H P(O)(OCH and dimethyl phosphite, HP(O) (OCH The free radical initiators which are employed in the process constitute a well known class of materials conventionally employed in reactions of the character involved. Such initiators, which are suitable for the present id as a dark heavy oil, completely soluble in absolute alcohol or water. Analysis.-Calculated for CI-[F14H3O3PI P, 7.16%; liequivalents of hydrogen ion/ g. 4.63. Found: P, 7.8% milliequivalents ofhydrogen ion/ g. 4.5.

Titration with standardized alkali gave pKa =2.8 for the first acid group and pKa =5.0 for the second acic group.

SURFACE TENSIONS OF AQUEOUS SOLUTIONS The surface tensions of aqueous solutions of the acid were measured at C. using a Du Nouy tensiometer. The solutions were allowed to stand for two hours after preparation before measurements were made. The re sults are shown below.

SURFACE TEN SIGNS OF AQUEOUS SOLUTIONS OF CFa CFz) 4CHFCF2P O) (OH)2 Cone, Wt. percent dynes/crn, 25 C compounds usually require temperatures of from 50 C. to about 100 C. The preferred'reaction temperature for the preferred di-tert.-butyl peroxide will be from about 115 C. to about 175 C.

When the phosphorus compound,

is such that Z is an alkyl or aryl group, the resulting product will be an ester. The esters are readily converted to the acids by treatment with a mineral acid, such as hydrochloric acid, preferably by refluxing the mixture of the ester and the mineral acid for a short time. The alkali metal salts also readily convert to the free acids by treat ment with a mineral acid, such as hydrochloric acid. Also, the free acids of this invention can be readily converted to the salts by treatment with a hydroxide, oxide, carbonate, or bicarbonate of the metal. The esters are also saponified by strong bases. The alkyl esters, in common with most alkyl esters of strong acids, decompose at elevated temperatures, although they can be distilled at reduced pressures. The esters are water insoluble but are soluble in hydrocarbons, halogenated hydrocarbons, and many other organic solvents.

In order to more clearly illustrate this invention, preferred modes of carrying them into effect and the advantageous results to be obtained thereby, the following examples are given in which the amounts and proportions are by weight except where specifically indicated otherwise.

EXAMPLE 1 Dimethyl Beta-Hydroperfluoroheptylphosphonate A silver lined 400 ml. shaker tube was charged with 150 g. (0.43 mole) of perfluoroheptened, 47.0 g. (0.43 mole) of dimethyl phosphite and 3.1 g. (0.02 mole) of ditert.-buty peroxide. The mixture was heated for one and one-half hours at 127 C.-176 C. while shaking. The product weighed 185 g. Distillation gave 104 g. (70% recovery) of unreacted perfluoroheptene-l, B.P. 82 C. The residue, remaining after removing excess dimethyl phosphite, weighed 41.0 .g. (20% conversion, 65% yield).

EXAMPLE 2 Beta-Hydroperfluoroheptylphosphonic Acid The residue from Example 1 was heated under reflux for several hours with concentrated hydrochloric acid. Evaporation of the volatile liquid left 26.0 g. of beta-hydroperfluoroheptylphosphonic acid,

cmcr ncnnon mo on SURFACE TENSIONS OF NONAQUEOUS SOLUTIONS A benzene solution of CF (CF CHFOF P(O) (OI-I; (0.043 Wt. percent) was found to have a surface tension 7 dynes/ cm. lower than benzene itself at 25 C.

With a benzene solution of omega-hydroperfluorooctylphosphonic acid, H(CF CF P(O) (OH) of concentration similar to the above solution, measurements indicated no change in the surface tension.

Kerosene, containing 0.1 wt. percent exhibits a surface tension of 6 to 8 dynes/cm. lower than kerosene itself, at 25 C.

When a 0.1 wt. percent solution of in kerosene was prepared, the surface tension was unchanged.

A 0.082 wt. percent solution of in 1,1,2-trifluoro-1,2,2-trichloroethane, CF ClCFCl at 25 C., exhibits a surface tension of 15.3 dynes/cm. 1,1,2-trifluoro-1,2,2-trichloroethane itself exhibits a surface tension of 17.6 dynes/cm. at 25 C.

A solution of H(CF CF P(O) (OH),, in 1,1,2-trifluoro-l,2,2-trichloroethane exhibits the same surface tension as the solvent itself. This w-hydro-compound does not dissolve to any apparent extent in the trifluorotrichloroethane.

Perfluorooctanoic acid, C F COOH, has no effect on the surface tension of 1,1,2-trichloro-1,2,2-trifluoroethane at any concentration up to and including the saturated solution.

EXAMPLE 3 Diethyl Beta-Hydroperfluoroheptylphosphonate A mixture of 00 g. (0.57 mole) of perfluoroheptene-l, 80.0 g. (0.57 mole) of diethyl phosphite and 4.4 g. of di-tert.-butyl peroxide was heated in a silver lined shaker tube at C. C. for two hours. The clear, tan product weighed 269 g. Distillation gave 100 g. of recovered perfluoroheptene-l, 19.0 g. of a mixture of the olefin and diethyl phosphite, and 37.0 g. of recovered diethyl phosphite. The product,

CF CF CHF CF 1 (0) (00 1-1 2 distilled at 76 C. at 4.0 mm. Hg pressure to 83 C, at 2.0 mm. pressure with some decomposition, n 1.3816 to 1.3466, 42.1 g. A residue, composed of 43.5 g, of CF (CF CHFCF P(O)(OI-D was also obtained.

The diethyl ester was redistilled, B.P. 105 C.l13 C. at 10.0 mm. pressure.

Analysis.Calculated for C F H O P: C, 27.05%;

7 F, 54.5%; P, 6.35%. Found: C, 29.3%; F, 50.4%; P, 5.9%.

EXAMPLE 4 Sodium Beza-Hydroperfluoroheptylphosphinate A mixture of 70.0 g, (0.20 mole) of perfluoroheptene-l, 21.2 g. (0.20 mole) of sodium hypophosphite monohydrate, 0.20 g. of di-tert.-butyl peroxide and 78 g. of tert.- butyl alcohol was heated for three hours at 115 C.140 C, The product weighed 145.0 g.

A portion of the product (10.0 g.) was evaporated to dryness giving 4.51 g. of soft, white solid, containing mostly sodium beta-hydroperfluoroheptylphosphinate,

H CF@(oFz)4OHFoF21 ()(0N9) and small amounts of sodium'hypophosphite and tertbutyl alcohol. The infrared spectrum showed an adsorption band at 4.2,u. due to the PH bond and a shoulder at 7.84u to 8.06 due to the P O bond. The expected, strong CF adsorptions Were also present,

Analysis.Calculated for c F H PO Naz P, 6.82%. Found: P, 6.8%.

The surface tension of aqueous solutions of the product are given below.

SURFACE TENSIONS, AQUEOUS SOLUTIONS OF I OF (CF2)4CHFC F2]? (0) (ONa) Cone, wt. percen 0. 0315 dynes/cm., 25 C.

When a 1% solution of the salt was converted to the free beta-hydroperfluoroheptylphosphinic acid by addition of hydrochloric acid, the surface tension decreased from 18.4 dynes/ctn. to 15.8 dynes/cm., indicating the greater surface activity of the free acid.

CF CHFCF -P(O) (OC H 2 B.P. 87 C. at 10 mm. pressure, 11 1.3606.

Analysis.Calculated for C7H11FGO3PZ C, 29.1%; F, 39.6%; H, 3.8%; P, 10.75%. Found: C, 29.4%; F, 37.6%; H, 4.0%; P, 11.3%.

EXAMPLE 6 Beta-Hydroperfluoropropyl Phosphonic Acid The ester, CF CHFCF P(O) (OC H from Example 5 was hydrolyzed to thee free acid by reflux with concentrated hydrochloric acid. The product was isolated in the same manner as described in Example 2.

The surface tensions of 0.1% by weight aqueous solutions of CF CHF CF P(O)(OH) at 25 C. was found to be 39 dynes/cm.

EXAMPLE 7 Fire Extinguishing Experiments A water soluiton containing 0.5 wt. percent of CF (CF CHFCF P(O) (01-1) 2 was prepared. The surface tension was found to be 15.7

dynes/cm. When this aqueous solution was sprayed on gasoline contained in a small aluminum cup, the aqueous solution was visually observed to mix with and spread over the gasoline whose surface tension was 20-22 dynes/crn. When pure water is sprayed on gasoline in the same cup, it does not mix or spread on the gasoline but rather collects into droplets and sinks under the gasoline.

When gasoline in a small aluminum cup is ignited and an aqueous solution containing 0.5 wt. percent of amon ,crrrcr rown is sprayed onto the burning gasoline, the flames are extinguished in 1 to 2 seconds. When 1% by weight of CF CF CHFCF PH(O) (OH) is dissolved in Water, the surface tension is about 15 dynes/cm. When this solution is sprayed onto gasoline burning in a small aluminum cup, the flames are extinguished in about 2 seconds.

When about a 1% by weight solution of in Water is sprayed onto gasoline burning in a small aluminum cup, the flames are not extinguished.

When a 1% by weight solution of CF3CHFCF2P 0 on 2 in water (having a surface tension of 39 dynes/cm.) is sprayed onto burning gasoline in a small aluminum cup, the flames are not extinguished.

When gasoline is ignited in a small aluminum cup and an aqueous solution containing 0.5% by weight of either perfluorooctanoic acid (C7F15CO2H) or perfluorooctanesulfonic acid (C3F17SO3H), is sprayed onto the burning gasoline, the flames are not extinguished.

When 1 by weight of H[CF CF P(O)(OH) is dissolved in water to produce the minimum surface tension available (22 dynes/cm.) and the resulting solution is sprayed onto gasoline burning in a small aluminum cup, the flames are not extinguished and sometimes flare up.

When a solution containing enough commercial soap to produce the minimum surface tension obtainable (28- 30 dynes/ cm.) or water itself is sprayed on gasoline burning in a small aluminum cup, the flames are not extinguished but almost invariably flare up.

It will be understood that the preceding examples have been given for illustrative purposes solely and that this invention is not limited to the specific embodiments described therein. On the other hand, it will be readily apparent to those skilled in the art that, subject to the limitations set forth in the general description, the materials, proportions, conditions and techniques employed may be widely varied without departing from the spirit or scope of this invention. I

From the preceding description, it will be apparent that this invention provides new beta-hydroperfiuoroalkyl phosphonic acids, beta-hydroperfluoroalkyl phosphinic acids, and salts of such acids, which have valuable new, beneficial properties, and more particularly are superior surface active agents and are particularly valuable for converting water to an effective fire extinguishing composition, especially for extinguishing hydrocarbon and like fires. Accordingly, this invention constitutes a valuable advance in and contribution to the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

I claim:

1. A compound of the formula CFflOFQnCHFCFPP O wherein n is an integer of from 2 to 5.

5. Beta-hydroperfluoroheptylphosphinic acid.

References Cited in the file of this patent UNITED STATES PATENTS Bittles et a1 July 10, 1951 Anthony et a1. May 15, 1956 Anthony et a1 May 15, 1956 Van Winkle Mar. 12, 1957 

1. A COMPOUND OF THE FORMULA 